Project Summary Lung infections by non-tuberculous mycobacteria (NTM) Mycobacterium avium and Mycobacterium abscessus are increasing in incidence. Diseases caused by both Mycobacteria are common in patients with chronic lung conditions, e.g., cystic fibrosis (CF), non-CF bronchiectasis and emphysema. The current clinical paradigm is to treat patients with M. avium or M. abscessus lung infections with combination therapy given orally or IV. Unfortunately, these therapies often fail, or patients do not tolerate them due to side-effects. Thus, there is a need to develop new anti-mycobacterial therapies with better efficacy and improved safety and tolerability. The overall objective of this project is to test if three novel preparations designed for maximum efficacy and tolerability in the lung (Ciprofloxacin for Inhalation, CFI, Lipoquin; Dual Release Ciprofloxacin for Inhalation, DRCFI, Linhaliq; and a recently invented ciprofloxacin nanocrystal liposome formulation), provide effective NTM therapy alone and/or in combination with other antimycobacterial agents using in vitro and in vivo models of M. avium and M. abscessus lung infection. All three formulations are comprised of ciprofloxacin encapsulated in liposomes, which provide sustained slow release of the ciprofloxacin in the lung from the liposome, allowing for once-daily dosing. The DRCFI formulation is a mixture of CFI and free ciprofloxacin. The rationale for developing DRCFI is to combine the advantages of an initial transient high concentration of free ciprofloxacin to increase maximum levels in the lung from the free ciprofloxacin component of DRCFI, followed by the slow release of ciprofloxacin from CFI (liposomal component). The nanocrystals release drug more slowly than the others. Aradigm has demonstrated other important advantages of these formulations: avid ingestion by macrophages leading to effective killing of intracellular NTM infections, and the ability to kill NTM even within biofilms formed by these organisms in the lung. The specific aims are: 1) for M avium complex infection, test efficacy of: a) CFI/DRCFI/nanocrystals in combination with standard therapies clarithromycin/ethambutol and amikacin in macrophage/biofilm test systems; b) aerosolized CFI/DRCFI/nanocrystals in combination with systemic clarithromycin/ethambutol and amikacin for lung infection in mice; c) impact of emergence of antibiotic resistance on efficacy; 2) for M abscessus infection, test efficacy of: a) CFI/DRCFI/nanocrystals in combination with standard of therapy linezolid/imipenem in macrophage/biofilm test systems; b) aerosolized CFI/DRCFI/nanocrystals in combination with standard therapies systemic linezolid/imipenem; and c) impact of emergence of antibiotic resistance on efficacy. If an efficacious treatment with CFI or DRCFI (alone or in combination with other drugs) is identified, clinical trials will start in patients with M. avium or M. abscessus lung infection, including those with HIV/AIDS. Aradigm has sufficient safety data in humans and animals to support long-term clinical trials in patients with CFI/DRCFI as well as sufficient cGMP manufacturing in place to support large-scale clinical trials.